1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the invention relates to a method of a semiconductor device, in which the process of forming element-isolating regions and the step of processing the substrate surface are improved. The invention also relates to a semiconductor substrate formed by performing this method.
2. Description of the Related Art
To manufacture a semiconductor device, element-isolating regions must be formed in the substrate to isolate elements from one another. To form shallow trench isolation (STI) regions, i.e., element-isolating regions isolation of one type, reaction ion etching (RIE) is carried out in most cases.
More specifically, the surface of an Si substrate is oxidized, forming a thin oxide film, a silicon nitride (SiN) film is deposited on the thin oxide film, and an oxide film (TEOS) film is deposited on the silicon nitride film. Using a resist pattern as mask, selective RIE is performed on the TEOS film. Next, using the TEOS film as mask, the nitride film is etched. Then, using the nitride film as mask, the thin oxide film and Si substrate are etched. Thereafter, the unnecessary parts of the nitride film and the unnecessary parts of the oxide film lying beneath the nitride film are removed. Then, an insulating film is deposited and buried in the STI regions formed in the substrate. (See Jpn. Pat. Appln. KOKAI Publication No. 2003-51536.)
Such a method is disadvantageous in some respects. First, many steps must be carried out to form element-isolating regions. The step of forming the TEOS film may not be performed. Even in this case, the steps that should be performed remain numerous. Second, plasma damages develop in the Si substrate when the Si substrate is subjected to dry etching such as RIE. If the damage remains in the sides of any element-isolating region, it will degrade the characteristics of transistors. In order to prevent the degradation of characteristics, a step may be performed to eliminate the damages, before the insulating film is buried in the STI regions. This increases the number of steps.
In order to increase the effective area for capacitors, trench capacitors may be formed by processing the Si substrate in the same way as in the step of forming STI regions. In this case, too, the number of manufacturing steps inevitably increases.
As described above, the conventional method is disadvantageous in two respects. First, many steps must be performed to form element-isolating regions such as STI regions or to process the surface of the Si substrate for forming trench capacitors. Second, the damages that have developed in the substrate due to RIE degrade the characteristics of elements.